In recent years, hybrid vehicles are receiving attention as environmentally friendly vehicles. As motive power sources, the hybrid vehicles incorporate, in addition to a conventional engine, a DC (Direct Current) power supply, an inverter, and a motor driven by the inverter.
With such a hybrid vehicle, the engine is started/stopped in accordance with the traveling condition of the vehicle. However, when the engine is repeatedly started/stopped frequently, the fuel efficiency becomes poor.
Japanese Patent Laying-Open No. 2000-205000 discloses a hybrid vehicle that can solve the above problem. In the hybrid vehicle, a traveling condition where acceleration/deceleration is frequently repeated is inferred, and in accordance with a result of inference, a threshold value for starting/stopping the engine is changed. According to the hybrid vehicle, unnecessary starting/stopping of the engine is prevented, and improvements in fuel efficiency and acceleration response can be achieved.
Driving characteristics are varied among the drivers. Some drivers demand acceleration feel, whereas the others demand fuel-economic driving, possibly without starting the engine even when accelerating the vehicle. On the other hand, in the hybrid vehicle disclosed by Japanese Patent Laying-Open No. 2000-205000, the threshold value of starting/stopping engine is uniformly changed according to the inference result of the traveling condition, irrespective of the driver's driving characteristics. Accordingly, there is a possibility that a traveling performance matching the driver's driving characteristics cannot be achieved.
In particular, in a hybrid vehicle in which an on-board DC power supply is chargeable using a power supply external to the vehicle (a commercial power supply), since the range where traveling is performed only by the motor while the engine is stopped is increased, there is a possibility that a driver who demands acceleration feel may feel that the power is insufficient when accelerating the vehicle.